The present invention relates to dry, solid compositions containing an organic titanate/amino alcohol reaction product plus a mono- or disaccharide or a polyhydric alcohol derivable from a monosaccharide. The compositions are useful in preparing thixotropic cements and fluid fracture formulations for use in oil and gas wells.
It has long been known that titanium esters react with high molecular weight hydroxyl-containing compounds so as to crosslink them and produce gels; J. Oil and Colour Chem. Assoc. 31, 405 (1948). However, the crosslinking reaction made through the use of simple alkyl esters of titanium proceeds too rapidly for most industrial uses. The crosslinking rate imparted by titanium esters can be depressed by combining a titanium ester with a variety of multifunctional compounds, including triethanolamine.
The reaction product of tetraisopropyl titanate (also known as tetraisopropoxytitanium) and triethanolamine, at a titanate:triethanolamine mol ratio of 1:2, finds several industrial uses. Among others, that reaction product is used to crosslink high molecular weight compounds (e.g., hydroxypropyl guar gum), and the crosslinked high molecular weight material is used to fracture oil-bearing formations; that type of use is disclosed in U.S. Pat. No. 3,888,312. The reaction product of tetraisopropyl titanate and triethanolamine, at a titanate:triethanolamine mol ratio of 1:1, has had little if any industrial use. On the other hand, it has been disclosed in U.S. Pat. No. 2,950,174.
In the preparation of both of the foregoing titanate:triethanolamine reaction products, 2-3 mols of isopropanol are liberated from the titanate and it is common to use or sell the reaction product without removing the isopropanol. On the other hand, it has been proposed to react the amino alcohol with the titanate, add a polyhydroxyorganic compound as a stabilizer, evaporate the alcohol liberated in the reaction between the titanate and the amino alcohol, and replace the evaporated alcohol with enough water to dissolve the stabilized amino alcohol:titanate reaction product; see U.S. Pat. No. 2,894,966.
The use of thixotropic cements in oil and gas wells is well known; see for example U.S. Pat. Nos. 2,890,752 and 3,804,174. In the former, Portland cement is combined with a hydrocarbon liquid and an alkali metal soap. In the latter, a hydraulic cement (such as Portland, aluminous or pozzolanic hydraulic cement) is combined with a cellulose ether and a salt of zirconium, lead, chromium, ferric iron, hafnium, lanthanum or yttrium, preferably zirconium oxychloride.
The compositions of the present invention provide a number of advantages over those disclosed heretofore. For example, zirconium oxychloride is more toxic than the titanium compounds; it adversely affects the set rate of the cement and does not effect thixotropy in cements over the broad range of temperatures normally encountered in most wells, viz. 60.degree.-135.degree. C. Similarly, the reaction product of tetraisopropyl titanate and triethanolamine at a titanate:triethanolamine molar ratio of 1:2 did not perform satisfactorily in cements at the lower temperatures, and it is a liquid whereas a solid is preferred for dry blending with cement. If one attempts to remove water and/or alcohol from the products of U.S. Pat. Nos. 2,894,966 and 2,950,174, gummy solids, e.g., having the consistency of molasses, are obtained. Moreover, the liquid products of those patents (e.g., Example VIII of the former and XXIII of the latter) do not effect thixotropy at 60.degree. C. as well as do the products of the invention.